Modeling of Pressure Retarded Osmosis Using the Q-Electrolattice Equation of State

The mixing of solutions of different salinities occurs in many practical situations. A large-scale example is the mixing of river water with seawater. Such mixing processes have attracted much attention as a potential renewable energy source through a membrane-based process known as pressure-retarded osmosis (PRO). The ultimate goal of PRO units is to convert the energy released by the mixing process into mechanical or electrical power. While many researchers agree that PRO processes based on the salinity difference between freshwater and seawater are unfeasible at current conditions, more study is necessary to assess the feasibility of processes based on streams of higher salinity. One such processes is the energy recovery from desalination units by taking advantage of the mixing of discharged brine and seawater. Another process is the mixing of seawater with high-salinity produced water from oil exploration. This thesis investigates the power that can be harvested from different mixing systems such as freshwater+seawater, brine+seawater, and produced-water+seawater by PRO. To assess the performance of PRO, it is necessary to predict various thermodynamic properties such as Gibbs free energy, osmotic pressure, molar volume, entropy, and enthalpy and to calculate water fluxes across the membrane accurately. The Q-electrolattice equation of state (EOS), which extends a lattice-based fluid model for electrolyte solutions, is adopted to estimate the thermodynamic properties of the electrolyte solutions. However, the behavior of water fluxes through the membrane unit is much complicated due to concentration polarization, fouling of membrane, and reverse salt flux. Recently two very useful equations have been proposed to estimate the water and salt fluxes across the membrane that consider all of them, but the problem is the implementation of these equations into the PRO calculation. Many models have been developed for PRO calculation, which calculates thermodynamic properties, water flux, and power outputs separately even though they are interdependent, thus introducing the possibility of inconsistent results. In addition, quite often, studies on this topic adopt correlations for these various properties and are based on solutions of Na⁺ and Cl¯ ions only while, in practice, the solutions contain many other ions. This work develops a model to estimate the power recovery from the mixing of two solutions of different salinities by incorporating mass flux equations with Q-electrolattice EOS, which is capable of estimating all necessary thermodynamic properties and determining water and salt fluxes and power density simultaneously in a single framework. Initial investigations have been done for the solutions of Na⁺ and Cl¯ ions only. Finally, the developed model is extended to solutions of multiple ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl¯ and SO²¯₄) and to multiple membrane systems

Rational Synthesis of Ultra-small and Durable Platinum-based Catalysts for Renewable Energy Applications

Ultrasmall supported platinum nanoparticles (Pt NPs) are often used in two promising renewable energy production technologies – hybrid-sulfur water splitting for actively catalyzing H2SO4 decomposition and in fuel cells for the oxygen reduction reaction (ORR). However, the stability of Pt NPs under reaction conditions is the ultimate challenge for these processes. Two prevalent ways to overcome this challenge are improving stability by anchoring Pt onto a secondary metal or doping heteroatoms into the support. This dissertation covers the rational design, synthesis, and stabilization of Pt-based catalysts in these two ways to achieve durable catalytic performance with desired activity and selectivity. The first vein of this research explores the stabilization of core-shell structured Ir-Pt bimetallic NPs on pre-stabilized titania (TiO2) or boron nitride (BN) support for high-temperature H2SO4 decomposition, particularly SO3 to SO2 decomposition. A series of Ir-Pt catalysts have been synthesized with different Ir loading and evaluated for the selective decomposition of SO3 to SO2 in an extreme (high temperature, highly corrosive) reaction environments. Investigations have revealed that the deactivation of Ir-Pt catalyst on pre-stabilized TiO2 is more dominant than BN, confirmed by X-ray diffraction and catalyst evaluation results. Furthermore, a negligible catalyst deactivation has been obtained for 1\%Pt-7.5\%Ir/BN. Various characterization techniques have been employed to explain this consistent stability. In the second vein of research, the stabilization of Pt NPs by nitrogen-doped carbon has been explored with a combination of high sensitivity X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) with in-situ pretreatment. The high sensitivity XRD instrument has allowed the incredibly observationed the behavior of ultrasmall Pt NPs (about 1 nm), which was previously impossible to observedetect. Furthermore, the XRD results have been clarified the unappreciated trend in the literature of why XRD peaks of ultrasmall Pt NPs often appear shifted to the left. Additionally, using XPS, this work has been corrected a prevalent literature delusion that higher valences of Pt in N-doped carbon result from the formation of Pt-N bond. In the final part of this work, the strong electrostatic interaction (SEA) technique has been explored to synthesize small, uniformly distributed, and highly dispersed Pt NPs on Vulcan XC72R carbon (Pt/C). The SEA method has significantly improved catalyst durability for ORR in proton-exchange membrane fuel cells (PEMFCs) by tuning metal-support interactions, confirmed by a comparative durability study in PEMFCs on various Pt/C catalysts prepared by dry and wet impregnation, polyol, and SEA methods. In addition, a thermal stability test has been performed based on these Pt/C catalysts that have validated the superiority SEA catalyst by demonstrating the metal-support interactions

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Adsorption Characteristics of Banana Peel in the Removal of Dyes from Textile Effluent

Disposal of reactive dye contaminants in surface waters causes serious health risks to the aquatic living bodies and populations adjacent to the polluted water sources. This study investigated the applicability of banana peels to remediate water contamination with reactive dyes used in the textile industry. A set of batch experiments was conducted using a standard dye solution to determine optimum adsorption parameters, and these parameters were used for the removal of dyes from actual wastewater. Fitting experimental data into the isotherm and kinetic models suggested monolayer dye adsorption with chemisorption rate-limiting step. The maximum adsorption found from modeling results was 28.8 mg/g. Fourier transformed infrared (FTIR) spectra revealed the existence of hydroxyl, amine and carboxylic groups, contributing to high adsorption of dye molecules onto the adsorbent surface. About 93% of the dyes from the standard solution were removed at optimum conditions (pH—7.0, initial dye concentration—100 mg/L, contact time—60 min, and adsorbent dose—0.5 g) while this value was 84.2% for industrial textile wastewater. This difference was mainly attributed to the composition difference between the solutions. However, the removal efficiency for actual wastewater is still significant, indicating the high potentiality of banana peel removing dyes from textile effluent. Furthermore, desorption studies showed about 95% of banana peel can be recovered with simple acid-base treatment

Preoperative nasopharyngeal swab testing and postoperative pulmonary complications in patients undergoing elective surgery during the SARS-CoV-2 pandemic.

BACKGROUND: Surgical services are preparing to scale up in areas affected by COVID-19. This study aimed to evaluate the association between preoperative SARS-CoV-2 testing and postoperative pulmonary complications in patients undergoing elective cancer surgery. METHODS: This international cohort study included adult patients undergoing elective surgery for cancer in areas affected by SARS-CoV-2 up to 19 April 2020. Patients suspected of SARS-CoV-2 infection before operation were excluded. The primary outcome measure was postoperative pulmonary complications at 30 days after surgery. Preoperative testing strategies were adjusted for confounding using mixed-effects models. RESULTS: Of 8784 patients (432 hospitals, 53 countries), 2303 patients (26.2 per cent) underwent preoperative testing: 1458 (16.6 per cent) had a swab test, 521 (5.9 per cent) CT only, and 324 (3.7 per cent) swab and CT. Pulmonary complications occurred in 3.9 per cent, whereas SARS-CoV-2 infection was confirmed in 2.6 per cent. After risk adjustment, having at least one negative preoperative nasopharyngeal swab test (adjusted odds ratio 0.68, 95 per cent confidence interval 0.68 to 0.98; P = 0.040) was associated with a lower rate of pulmonary complications. Swab testing was beneficial before major surgery and in areas with a high 14-day SARS-CoV-2 case notification rate, but not before minor surgery or in low-risk areas. To prevent one pulmonary complication, the number needed to swab test before major or minor surgery was 18 and 48 respectively in high-risk areas, and 73 and 387 in low-risk areas. CONCLUSION: Preoperative nasopharyngeal swab testing was beneficial before major surgery and in high SARS-CoV-2 risk areas. There was no proven benefit of swab testing before minor surgery in low-risk areas

Delaying surgery for patients with a previous SARS-CoV-2 infection

Not availabl

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background: Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods: This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was coprioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low-middle-income countries. Results: In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of 'single-use' consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low-middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion: This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high- and low-middle-income countries